The utility model relates to a three-switch level detector which belongs to a water level detecting device. The structure of the utility model is composed of a measuring device with three switches and a microcomputer control circuit, wherein, the three switches are arranged on a speed reduction box and are driven by a rotary guide wheel. A rope is arranged on the guide wheel, and both ends of the rope are added with a floating ball and a heavy hammer. When the liquid level changes one centimeter (increase or reduce), the switch is switched on or switched off in one time correspondingly. Thus, the corresponding switching-on or switching-off change of the triple switch is converted into the microcomputer for data processing, and the current value of the liquid level can be judged. The utility model has the advantages that the work is realized by the three switches of the float to replace the complicated code disc and the coded counting equipment, the structure is simple, and the stability and the reliability are realized.